Devices using inductive hob heating for cooking containers are known from the prior art. In this case, the hob heating inside the cooking plate comprises an induction coil through which a high-frequency alternating current flows. This alternating current induces a rapidly varying magnetic field which is guided in the direction of the container. The alternating magnetic field induces an electric voltage inside the base of the container, which is embodied as ferromagnetic, which in turn results in the formation of an eddy current (induction current) which brings about heating of the bottom of the pot. One of the advantages of this type of inductive hob heating is that merely the bottom of the pot and no other energy-storing parts such as the cooking plate, for example, are heated. Consequently, the user cannot burn himself on the cooking plate.
DE 42 24 405 A1 describes an inductive hob heating system of this type which is located underneath a cooking plate, especially a glass ceramic plate and consists of a cohesive assembly containing two induction coils located in a tray. The induction coils are constructed as flat-disk-shaped and are supported by means of thermal insulation on the underside of the glass ceramic plate and by means of a ferrite plate on a heat sink. One of the disadvantages of this type of inductive hob heating system is that the efficiency is negatively influenced by scattering losses of the electric magnetic field. Further losses occur during passage of the magnetic field through the cooking plate so that known inductive hob heating systems can attain a maximum efficiency of around 60%.
Known from DE 100 31 167 A1 is an arrangement for cooking food comprising a cooking surface with a cooking zone to which a first heating element is allocated. A cooking device which can be heated by the first heating element can be placed on the cooking zone, wherein the cooking device comprises a second heating element. In this case, an electrical connection is provided on the cooking surface to which the cooking device with the second heating element can be connected. The advantage of this arrangement is that the cooking device can be heated directly by “active heating” which has a positive effect with regard to the efficiency. A disadvantage however is that the second heating element is connected by means of a cable to the electrical connection. The cable running from the cooking device in the direction of the cable can be disturbing for the use during cooking food, in particular the user can get caught in the cable as a result of any inattentive movement with the consequence that the cooking device can tip.
Known from U.S. Pat. No. 4,996,405 is a device wherein a secondary winding formed from a current conductor and a heating element connected to the winding are located in a base element. The energy for the heating element is transferred from a primary winding which is disposed in a device for the transmission of energy, to the secondary winding by means of induction. One of the disadvantages is that these devices have a relatively large volume with the result that the arrangement of the device in the base element of a pot results in a large-volume pot.